Commercial aircraft typically include a plurality of air data systems for monitoring certain critical parameters used in controlling the aircraft. In the conventional arrangement, separate air data systems are provided for the airframe (i.e., cockpit instrumentation) and the electronic engine controls. The airframe air data system drives cockpit displays related to the navigation and flight condition of the aircraft, e.g., indicating altitude, rate of climb, air speed, and Mach number; the electronic engine controls use similar sensor data to regulate the air/fuel ratio and other variables affecting the engines. To insure fail-safe operation of the aircraft, redundant total pressure, total temperature, and static pressure sensors are provided for each air data system and each electronic engine control system.
Sensors for the airframe air data system are normally disposed on or in the fuselage of the aircraft, while those that service the electronic engine control systems are disposed in each engine pod. Although the engine and airframe air data systems monitor the same parameters in prior art designs, there is typically no communication of data between each of the discrete air data systems, nor any attempt to select a single best value of any of the common parameters for use by all air data systems on the aircraft.
In the past, aircraft design engineers have been reluctant to combine the various air data systems into an integrated system, due to the need to maintain independent fault accommodation in each engine. A guiding principle applied in designing critical aircraft systems is that no single failure of a component should result in any undesired effect on more than one engine. However, there are significant advantages in using common air data for the airframe and the electronic engine control systems. For example, if the same air data are used, the thrust ratings computed by the cockpit flight management system will agree with those determined by each of the electronic engine control systems, and the performance of the engines will be more accurately matched to each other. Often, in conventional designs, there are significant variations between common parameters separately determined by each system. Perhaps more importantly, communication of data between the various air data systems is likely to provide an even more effective fail-safe system than the conventional approach by increasing the level of sensor redundancy.
These and other objects and advantages of the present invention will be apparent from the attached drawings and the Description of the Preferred Embodiment that follows.